From 0487c1d701c401c66f42cb57b3760134ec672e8a Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Fri, 24 Sep 2021 11:52:54 -0600
Subject: [PATCH 01/12] Fix the use_frozen_modules value in test_embed.

---
 Lib/test/test_embed.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_embed.py b/Lib/test/test_embed.py
index e1b466a7b56b18..cda814c3ed34ee 100644
--- a/Lib/test/test_embed.py
+++ b/Lib/test/test_embed.py
@@ -434,7 +434,7 @@ class InitConfigTests(EmbeddingTestsMixin, unittest.TestCase):
         'pathconfig_warnings': 1,
         '_init_main': 1,
         '_isolated_interpreter': 0,
-        'use_frozen_modules': False,
+        'use_frozen_modules': 0,
     }
     if MS_WINDOWS:
         CONFIG_COMPAT.update({

From aa840cadbd45708a77b6bf0559a308de1305ac90 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Tue, 31 Aug 2021 15:54:15 -0600
Subject: [PATCH 02/12] Add _Py_GetMainConfig().

---
 Include/internal/pycore_pystate.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Include/internal/pycore_pystate.h b/Include/internal/pycore_pystate.h
index 4b894f3eff4967..aef318989aa6e5 100644
--- a/Include/internal/pycore_pystate.h
+++ b/Include/internal/pycore_pystate.h
@@ -30,6 +30,17 @@ _Py_IsMainInterpreter(PyInterpreterState *interp)
 }
 
 
+static inline const PyConfig *
+_Py_GetMainConfig(void)
+{
+    PyInterpreterState *interp = _PyRuntime.interpreters.main;
+    if (interp == NULL) {
+        return NULL;
+    }
+    return _PyInterpreterState_GetConfig(interp);
+}
+
+
 /* Only handle signals on the main thread of the main interpreter. */
 static inline int
 _Py_ThreadCanHandleSignals(PyInterpreterState *interp)

From 58a73876b79ba7b4491ca418233e9b35b984b4c0 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Wed, 22 Sep 2021 09:38:45 -0600
Subject: [PATCH 03/12] Factor out _Py_join_relfile() and _Py_add_relfile().

---
 Include/internal/pycore_fileutils.h |  6 +++
 Modules/getpath.c                   | 42 ++++-------------
 PC/getpathp.c                       |  3 +-
 Python/fileutils.c                  | 72 +++++++++++++++++++++++++++++
 4 files changed, 88 insertions(+), 35 deletions(-)

diff --git a/Include/internal/pycore_fileutils.h b/Include/internal/pycore_fileutils.h
index c1c9244a1bc7c4..c39ae7286b462e 100644
--- a/Include/internal/pycore_fileutils.h
+++ b/Include/internal/pycore_fileutils.h
@@ -65,6 +65,12 @@ extern int _Py_EncodeNonUnicodeWchar_InPlace(
     Py_ssize_t size);
 #endif
 
+extern wchar_t * _Py_join_relfile(const wchar_t *dirname,
+                                  const wchar_t *relfile);
+extern int _Py_add_relfile(wchar_t *dirname,
+                           const wchar_t *relfile,
+                           size_t bufsize);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/Modules/getpath.c b/Modules/getpath.c
index 363d62a0657ebd..7979359116bf27 100644
--- a/Modules/getpath.c
+++ b/Modules/getpath.c
@@ -235,28 +235,18 @@ isdir(const wchar_t *filename)
 static PyStatus
 joinpath(wchar_t *path, const wchar_t *path2, size_t path_len)
 {
-    size_t n;
-    if (!_Py_isabs(path2)) {
-        n = wcslen(path);
-        if (n >= path_len) {
+    if (_Py_isabs(path2)) {
+        if (wcslen(path2) >= path_len) {
             return PATHLEN_ERR();
         }
-
-        if (n > 0 && path[n-1] != SEP) {
-            path[n++] = SEP;
-        }
+        wcscpy(path, path2);
     }
     else {
-        n = 0;
-    }
-
-    size_t k = wcslen(path2);
-    if (n + k >= path_len) {
-        return PATHLEN_ERR();
+        if (_Py_add_relfile(path, path2, path_len) < 0) {
+            return PATHLEN_ERR();
+        }
+        return _PyStatus_OK();
     }
-    wcsncpy(path + n, path2, k);
-    path[n + k] = '\0';
-
     return _PyStatus_OK();
 }
 
@@ -283,23 +273,7 @@ joinpath2(const wchar_t *path, const wchar_t *path2)
     if (_Py_isabs(path2)) {
         return _PyMem_RawWcsdup(path2);
     }
-
-    size_t len = wcslen(path);
-    int add_sep = (len > 0 && path[len - 1] != SEP);
-    len += add_sep;
-    len += wcslen(path2);
-
-    wchar_t *new_path = PyMem_RawMalloc((len + 1) * sizeof(wchar_t));
-    if (new_path == NULL) {
-        return NULL;
-    }
-
-    wcscpy(new_path, path);
-    if (add_sep) {
-        wcscat(new_path, separator);
-    }
-    wcscat(new_path, path2);
-    return new_path;
+    return _Py_join_relfile(path, path2);
 }
 
 
diff --git a/PC/getpathp.c b/PC/getpathp.c
index 603a1eb13c4ff0..72427895902ec8 100644
--- a/PC/getpathp.c
+++ b/PC/getpathp.c
@@ -82,6 +82,7 @@
 #include "Python.h"
 #include "pycore_initconfig.h"    // PyStatus
 #include "pycore_pathconfig.h"    // _PyPathConfig
+#include "pycore_fileutils.h"     // _Py_add_relfile()
 #include "osdefs.h"               // SEP, ALTSEP
 #include <wchar.h>
 
@@ -253,7 +254,7 @@ ismodule(wchar_t *filename, int update_filename)
 static void
 join(wchar_t *buffer, const wchar_t *stuff)
 {
-    if (FAILED(PathCchCombineEx(buffer, MAXPATHLEN+1, buffer, stuff, 0))) {
+    if (_Py_add_relfile(buffer, stuff, MAXPATHLEN+1) < 0) {
         Py_FatalError("buffer overflow in getpathp.c's join()");
     }
 }
diff --git a/Python/fileutils.c b/Python/fileutils.c
index 9e732ddca55cec..7b0cfd6d703775 100644
--- a/Python/fileutils.c
+++ b/Python/fileutils.c
@@ -7,6 +7,7 @@
 #ifdef MS_WINDOWS
 #  include <malloc.h>
 #  include <windows.h>
+#  include <pathcch.h>            // PathCchCombineEx
 extern int winerror_to_errno(int);
 #endif
 
@@ -2072,6 +2073,77 @@ _Py_abspath(const wchar_t *path, wchar_t **abspath_p)
 }
 
 
+// The caller must ensure "buffer" is big enough.
+static int
+join_relfile(wchar_t *buffer, size_t bufsize,
+             const wchar_t *dirname, const wchar_t *relfile)
+{
+    assert(!_Py_isabs(relfile));
+#ifdef MS_WINDOWS
+    if (FAILED(PathCchCombineEx(buffer, bufsize, dirname, relfile, 0))) {
+        return -1;
+    }
+#else
+    size_t dirlen = wcslen(dirname);
+    size_t rellen = wcslen(relfile);
+    size_t maxlen = bufsize - 1;
+    if (maxlen > MAXPATHLEN || dirlen >= maxlen || rellen >= maxlen - dirlen) {
+        return -1;
+    }
+    if (dirlen == 0) {
+        // We do not add a leading separator.
+        wcscpy(buffer, relfile);
+    }
+    else {
+        if (dirname != buffer) {
+            wcscpy(buffer, dirname);
+        }
+        size_t relstart = dirlen;
+        if (dirlen > 1 && dirname[dirlen - 1] != SEP) {
+            buffer[dirlen] = SEP;
+            relstart += 1;
+        }
+        wcscpy(&buffer[relstart], relfile);
+    }
+#endif
+    return 0;
+}
+
+/* Join the two paths together, like os.path.join().  Return NULL
+   if memory could not be allocated.  The caller is responsible
+   for calling PyMem_RawFree() on the result. */
+wchar_t *
+_Py_join_relfile(const wchar_t *dirname, const wchar_t *relfile)
+{
+    assert(dirname != NULL && relfile != NULL);
+    assert(!_Py_isabs(relfile));
+    size_t maxlen = wcslen(dirname) + 1 + wcslen(relfile);
+    size_t bufsize = maxlen + 1;
+    wchar_t *filename = PyMem_RawMalloc(bufsize * sizeof(wchar_t));
+    if (filename == NULL) {
+        return NULL;
+    }
+    assert(wcslen(dirname) < MAXPATHLEN);
+    assert(wcslen(relfile) < MAXPATHLEN - wcslen(dirname));
+    join_relfile(filename, bufsize, dirname, relfile);
+    return filename;
+}
+
+/* Join the two paths together, like os.path.join().
+     dirname: the target buffer with the dirname already in place,
+              including trailing NUL
+     relfile: this must be a relative path
+     bufsize: total allocated size of the buffer
+   Return -1 if anything is wrong with the path lengths. */
+int
+_Py_add_relfile(wchar_t *dirname, const wchar_t *relfile, size_t bufsize)
+{
+    assert(dirname != NULL && relfile != NULL);
+    assert(bufsize > 0);
+    return join_relfile(dirname, bufsize, dirname, relfile);
+}
+
+
 /* Get the current directory. buflen is the buffer size in wide characters
    including the null character. Decode the path from the locale encoding.
 

From e19a40a7edffecef96d449e8e669c86d48a6af6c Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Wed, 22 Sep 2021 09:47:59 -0600
Subject: [PATCH 04/12] Move DECODE_LOCALE_ERR to the internal API.

---
 Include/internal/pycore_fileutils.h |  6 ++++++
 Modules/getpath.c                   |  5 -----
 Python/initconfig.c                 |  5 -----
 Python/preconfig.c                  | 10 ++--------
 4 files changed, 8 insertions(+), 18 deletions(-)

diff --git a/Include/internal/pycore_fileutils.h b/Include/internal/pycore_fileutils.h
index c39ae7286b462e..8125ca7e982208 100644
--- a/Include/internal/pycore_fileutils.h
+++ b/Include/internal/pycore_fileutils.h
@@ -10,6 +10,12 @@ extern "C" {
 
 #include <locale.h>   /* struct lconv */
 
+// This is used after getting NULL back from Py_DecodeLocale().
+#define DECODE_LOCALE_ERR(NAME, LEN) \
+    ((LEN) == (size_t)-2) \
+     ? _PyStatus_ERR("cannot decode " NAME) \
+     : _PyStatus_NO_MEMORY()
+
 PyAPI_DATA(int) _Py_HasFileSystemDefaultEncodeErrors;
 
 PyAPI_FUNC(int) _Py_DecodeUTF8Ex(
diff --git a/Modules/getpath.c b/Modules/getpath.c
index 7979359116bf27..6229437ea686de 100644
--- a/Modules/getpath.c
+++ b/Modules/getpath.c
@@ -115,11 +115,6 @@ extern "C" {
 
 #define BUILD_LANDMARK L"Modules/Setup.local"
 
-#define DECODE_LOCALE_ERR(NAME, LEN) \
-    ((LEN) == (size_t)-2) \
-     ? _PyStatus_ERR("cannot decode " NAME) \
-     : _PyStatus_NO_MEMORY()
-
 #define PATHLEN_ERR() _PyStatus_ERR("path configuration: path too long")
 
 typedef struct {
diff --git a/Python/initconfig.c b/Python/initconfig.c
index 8740cc1cf7a2b3..40a5846f43b735 100644
--- a/Python/initconfig.c
+++ b/Python/initconfig.c
@@ -587,11 +587,6 @@ Py_GetArgcArgv(int *argc, wchar_t ***argv)
 
 /* --- PyConfig ---------------------------------------------- */
 
-#define DECODE_LOCALE_ERR(NAME, LEN) \
-    (((LEN) == -2) \
-     ? _PyStatus_ERR("cannot decode " NAME) \
-     : _PyStatus_NO_MEMORY())
-
 #define MAX_HASH_SEED 4294967295UL
 
 
diff --git a/Python/preconfig.c b/Python/preconfig.c
index ae1cc3f90fca7f..d59273159a6711 100644
--- a/Python/preconfig.c
+++ b/Python/preconfig.c
@@ -1,4 +1,5 @@
 #include "Python.h"
+#include "pycore_fileutils.h"     // DECODE_LOCALE_ERR
 #include "pycore_getopt.h"        // _PyOS_GetOpt()
 #include "pycore_initconfig.h"    // _PyArgv
 #include "pycore_pymem.h"         // _PyMem_GetAllocatorName()
@@ -6,12 +7,6 @@
 #include <locale.h>               // setlocale()
 
 
-#define DECODE_LOCALE_ERR(NAME, LEN) \
-    (((LEN) == -2) \
-     ? _PyStatus_ERR("cannot decode " NAME) \
-     : _PyStatus_NO_MEMORY())
-
-
 /* Forward declarations */
 static void
 preconfig_copy(PyPreConfig *config, const PyPreConfig *config2);
@@ -87,8 +82,7 @@ _PyArgv_AsWstrList(const _PyArgv *args, PyWideStringList *list)
             wchar_t *arg = Py_DecodeLocale(args->bytes_argv[i], &len);
             if (arg == NULL) {
                 _PyWideStringList_Clear(&wargv);
-                return DECODE_LOCALE_ERR("command line arguments",
-                                         (Py_ssize_t)len);
+                return DECODE_LOCALE_ERR("command line arguments", len);
             }
             wargv.items[i] = arg;
             wargv.length++;

From bae94c3b8d165c47d6e062a91d60112d1a3a9378 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Wed, 22 Sep 2021 11:37:40 -0600
Subject: [PATCH 05/12] Move _Py_wstat() to the internal API.

---
 Include/internal/pycore_fileutils.h |  3 +++
 Modules/getpath.c                   | 17 ----------------
 Python/fileutils.c                  | 30 +++++++++++++++++++++++++----
 3 files changed, 29 insertions(+), 21 deletions(-)

diff --git a/Include/internal/pycore_fileutils.h b/Include/internal/pycore_fileutils.h
index 8125ca7e982208..8491ed9b5ffe20 100644
--- a/Include/internal/pycore_fileutils.h
+++ b/Include/internal/pycore_fileutils.h
@@ -39,6 +39,9 @@ PyAPI_FUNC(wchar_t*) _Py_DecodeUTF8_surrogateescape(
     Py_ssize_t arglen,
     size_t *wlen);
 
+extern int
+_Py_wstat(const wchar_t *, struct stat *);
+
 PyAPI_FUNC(int) _Py_GetForceASCII(void);
 
 /* Reset "force ASCII" mode (if it was initialized).
diff --git a/Modules/getpath.c b/Modules/getpath.c
index 6229437ea686de..de1c6e3fbb657b 100644
--- a/Modules/getpath.c
+++ b/Modules/getpath.c
@@ -144,23 +144,6 @@ static const wchar_t delimiter[2] = {DELIM, '\0'};
 static const wchar_t separator[2] = {SEP, '\0'};
 
 
-/* Get file status. Encode the path to the locale encoding. */
-static int
-_Py_wstat(const wchar_t* path, struct stat *buf)
-{
-    int err;
-    char *fname;
-    fname = _Py_EncodeLocaleRaw(path, NULL);
-    if (fname == NULL) {
-        errno = EINVAL;
-        return -1;
-    }
-    err = stat(fname, buf);
-    PyMem_RawFree(fname);
-    return err;
-}
-
-
 static void
 reduce(wchar_t *dir)
 {
diff --git a/Python/fileutils.c b/Python/fileutils.c
index 7b0cfd6d703775..0e7c5b0084411f 100644
--- a/Python/fileutils.c
+++ b/Python/fileutils.c
@@ -1206,6 +1206,31 @@ _Py_fstat(int fd, struct _Py_stat_struct *status)
     return 0;
 }
 
+/* Like _Py_stat() but with a raw filename. */
+int
+_Py_wstat(const wchar_t* path, struct stat *buf)
+{
+    int err;
+#ifdef MS_WINDOWS
+    struct _stat wstatbuf;
+    err = _wstat(path, &wstatbuf);
+    if (!err) {
+        buf->st_mode = wstatbuf.st_mode;
+    }
+#else
+    char *fname;
+    fname = _Py_EncodeLocaleRaw(path, NULL);
+    if (fname == NULL) {
+        errno = EINVAL;
+        return -1;
+    }
+    err = stat(fname, buf);
+    PyMem_RawFree(fname);
+#endif
+    return err;
+}
+
+
 /* Call _wstat() on Windows, or encode the path to the filesystem encoding and
    call stat() otherwise. Only fill st_mode attribute on Windows.
 
@@ -1217,7 +1242,6 @@ _Py_stat(PyObject *path, struct stat *statbuf)
 {
 #ifdef MS_WINDOWS
     int err;
-    struct _stat wstatbuf;
 
 #if USE_UNICODE_WCHAR_CACHE
     const wchar_t *wpath = _PyUnicode_AsUnicode(path);
@@ -1227,9 +1251,7 @@ _Py_stat(PyObject *path, struct stat *statbuf)
     if (wpath == NULL)
         return -2;
 
-    err = _wstat(wpath, &wstatbuf);
-    if (!err)
-        statbuf->st_mode = wstatbuf.st_mode;
+    err = _Py_wstat(wpath, statbuf);
 #if !USE_UNICODE_WCHAR_CACHE
     PyMem_Free(wpath);
 #endif /* USE_UNICODE_WCHAR_CACHE */

From 7eea1bfd2c0ae2cc3f02d2dfcae9b4eae37bb884 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Fri, 24 Sep 2021 13:41:30 -0600
Subject: [PATCH 06/12] Do not pass the landmark to gotlandmark().

---
 PC/getpathp.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/PC/getpathp.c b/PC/getpathp.c
index 72427895902ec8..a4695da90c90f2 100644
--- a/PC/getpathp.c
+++ b/PC/getpathp.c
@@ -116,10 +116,6 @@
  * with a semicolon separated path prior to calling Py_Initialize.
  */
 
-#ifndef LANDMARK
-#  define LANDMARK L"lib\\os.py"
-#endif
-
 #define INIT_ERR_BUFFER_OVERFLOW() _PyStatus_ERR("buffer overflow")
 
 
@@ -279,12 +275,15 @@ canonicalize(wchar_t *buffer, const wchar_t *path)
    'prefix' is null terminated in bounds.  join() ensures
    'landmark' can not overflow prefix if too long. */
 static int
-gotlandmark(const wchar_t *prefix, const wchar_t *landmark)
+gotlandmark(const wchar_t *prefix)
 {
     wchar_t filename[MAXPATHLEN+1];
     memset(filename, 0, sizeof(filename));
     wcscpy_s(filename, Py_ARRAY_LENGTH(filename), prefix);
-    join(filename, landmark);
+#ifndef LANDMARK
+#  define LANDMARK L"lib\\os.py"
+#endif
+    join(filename, LANDMARK);
     return ismodule(filename, FALSE);
 }
 
@@ -292,12 +291,12 @@ gotlandmark(const wchar_t *prefix, const wchar_t *landmark)
 /* assumes argv0_path is MAXPATHLEN+1 bytes long, already \0 term'd.
    assumption provided by only caller, calculate_path() */
 static int
-search_for_prefix(wchar_t *prefix, const wchar_t *argv0_path, const wchar_t *landmark)
+search_for_prefix(wchar_t *prefix, const wchar_t *argv0_path)
 {
     /* Search from argv0_path, until landmark is found */
     wcscpy_s(prefix, MAXPATHLEN + 1, argv0_path);
     do {
-        if (gotlandmark(prefix, landmark)) {
+        if (gotlandmark(prefix)) {
             return 1;
         }
         reduce(prefix);
@@ -759,7 +758,7 @@ calculate_home_prefix(PyCalculatePath *calculate,
             reduce(prefix);
             calculate->home = prefix;
         }
-        else if (search_for_prefix(prefix, argv0_path, LANDMARK)) {
+        else if (search_for_prefix(prefix, argv0_path)) {
             calculate->home = prefix;
         }
         else {
@@ -937,7 +936,7 @@ calculate_module_search_path(PyCalculatePath *calculate,
             lookBuf[nchars] = L'\0';
             /* Up one level to the parent */
             reduce(lookBuf);
-            if (search_for_prefix(prefix, lookBuf, LANDMARK)) {
+            if (search_for_prefix(prefix, lookBuf)) {
                 break;
             }
             /* If we are out of paths to search - give up */

From 8876b27b81efaedf47343b92f667f71a23ce4922 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Fri, 24 Sep 2021 13:47:56 -0600
Subject: [PATCH 07/12] Drop the "update_filename" arg.

---
 PC/getpathp.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/PC/getpathp.c b/PC/getpathp.c
index a4695da90c90f2..02fd533278bef1 100644
--- a/PC/getpathp.c
+++ b/PC/getpathp.c
@@ -213,7 +213,7 @@ exists(const wchar_t *filename)
    Assumes 'filename' MAXPATHLEN+1 bytes long -
    may extend 'filename' by one character. */
 static int
-ismodule(wchar_t *filename, int update_filename)
+ismodule(wchar_t *filename)
 {
     size_t n;
 
@@ -228,9 +228,8 @@ ismodule(wchar_t *filename, int update_filename)
         filename[n] = L'c';
         filename[n + 1] = L'\0';
         exist = exists(filename);
-        if (!update_filename) {
-            filename[n] = L'\0';
-        }
+        // Drop the 'c' we just added.
+        filename[n] = L'\0';
         return exist;
     }
     return 0;
@@ -284,7 +283,7 @@ gotlandmark(const wchar_t *prefix)
 #  define LANDMARK L"lib\\os.py"
 #endif
     join(filename, LANDMARK);
-    return ismodule(filename, FALSE);
+    return ismodule(filename);
 }
 
 

From dcfe6153db995dbb77f589ea5a020d7e2f9d4aa3 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Fri, 24 Sep 2021 13:52:20 -0600
Subject: [PATCH 08/12] Drop gotlandmark().

---
 PC/getpathp.c | 30 +++++++++++-------------------
 1 file changed, 11 insertions(+), 19 deletions(-)

diff --git a/PC/getpathp.c b/PC/getpathp.c
index 02fd533278bef1..49864c49814681 100644
--- a/PC/getpathp.c
+++ b/PC/getpathp.c
@@ -270,32 +270,24 @@ canonicalize(wchar_t *buffer, const wchar_t *path)
 }
 
 
-/* gotlandmark only called by search_for_prefix, which ensures
-   'prefix' is null terminated in bounds.  join() ensures
-   'landmark' can not overflow prefix if too long. */
+/* assumes argv0_path is MAXPATHLEN+1 bytes long, already \0 term'd.
+   assumption provided by only caller, calculate_path() */
 static int
-gotlandmark(const wchar_t *prefix)
+search_for_prefix(wchar_t *prefix, const wchar_t *argv0_path)
 {
     wchar_t filename[MAXPATHLEN+1];
     memset(filename, 0, sizeof(filename));
-    wcscpy_s(filename, Py_ARRAY_LENGTH(filename), prefix);
+    /* Search from argv0_path, until LANDMARK is found.
+       We guarantee 'prefix' is null terminated in bounds. */
+    wcscpy_s(prefix, MAXPATHLEN+1, argv0_path);
+    do {
+        wcscpy_s(filename, Py_ARRAY_LENGTH(filename), prefix);
 #ifndef LANDMARK
 #  define LANDMARK L"lib\\os.py"
 #endif
-    join(filename, LANDMARK);
-    return ismodule(filename);
-}
-
-
-/* assumes argv0_path is MAXPATHLEN+1 bytes long, already \0 term'd.
-   assumption provided by only caller, calculate_path() */
-static int
-search_for_prefix(wchar_t *prefix, const wchar_t *argv0_path)
-{
-    /* Search from argv0_path, until landmark is found */
-    wcscpy_s(prefix, MAXPATHLEN + 1, argv0_path);
-    do {
-        if (gotlandmark(prefix)) {
+       /* join() ensures 'landmark' can not overflow prefix if too long. */
+        join(filename, LANDMARK);
+        if (ismodule(filename)) {
             return 1;
         }
         reduce(prefix);

From 1b05589e1143d53073208d40376c6a14e05b39ce Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Fri, 24 Sep 2021 14:04:51 -0600
Subject: [PATCH 09/12] Factor out is_stdlibdir().

---
 PC/getpathp.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/PC/getpathp.c b/PC/getpathp.c
index 49864c49814681..7495501a89944f 100644
--- a/PC/getpathp.c
+++ b/PC/getpathp.c
@@ -269,25 +269,32 @@ canonicalize(wchar_t *buffer, const wchar_t *path)
     return _PyStatus_OK();
 }
 
+static int
+is_stdlibdir(wchar_t *stdlibdir)
+{
+    wchar_t *filename = stdlibdir;
+#ifndef LANDMARK
+#  define LANDMARK L"os.py"
+#endif
+    /* join() ensures 'landmark' can not overflow prefix if too long. */
+    join(filename, LANDMARK);
+    return ismodule(filename);
+}
 
 /* assumes argv0_path is MAXPATHLEN+1 bytes long, already \0 term'd.
    assumption provided by only caller, calculate_path() */
 static int
 search_for_prefix(wchar_t *prefix, const wchar_t *argv0_path)
 {
-    wchar_t filename[MAXPATHLEN+1];
-    memset(filename, 0, sizeof(filename));
+    wchar_t stdlibdir[MAXPATHLEN+1];
     /* Search from argv0_path, until LANDMARK is found.
        We guarantee 'prefix' is null terminated in bounds. */
     wcscpy_s(prefix, MAXPATHLEN+1, argv0_path);
     do {
-        wcscpy_s(filename, Py_ARRAY_LENGTH(filename), prefix);
-#ifndef LANDMARK
-#  define LANDMARK L"lib\\os.py"
-#endif
-       /* join() ensures 'landmark' can not overflow prefix if too long. */
-        join(filename, LANDMARK);
-        if (ismodule(filename)) {
+        memset(stdlibdir, 0, sizeof(stdlibdir));
+        wcscpy_s(stdlibdir, Py_ARRAY_LENGTH(stdlibdir), prefix);
+        join(stdlibdir, L"lib");
+        if (is_stdlibdir(stdlibdir)) {
             return 1;
         }
         reduce(prefix);

From e05fdfd32391527ab2b4e4d5aa0ac83e05246f2d Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Fri, 24 Sep 2021 14:10:57 -0600
Subject: [PATCH 10/12] Do not call join() in each iteration.

---
 PC/getpathp.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/PC/getpathp.c b/PC/getpathp.c
index 7495501a89944f..6c82db4e9f65a9 100644
--- a/PC/getpathp.c
+++ b/PC/getpathp.c
@@ -286,14 +286,20 @@ is_stdlibdir(wchar_t *stdlibdir)
 static int
 search_for_prefix(wchar_t *prefix, const wchar_t *argv0_path)
 {
-    wchar_t stdlibdir[MAXPATHLEN+1];
     /* Search from argv0_path, until LANDMARK is found.
        We guarantee 'prefix' is null terminated in bounds. */
     wcscpy_s(prefix, MAXPATHLEN+1, argv0_path);
+    wchar_t stdlibdir[MAXPATHLEN+1];
+    memset(stdlibdir, 0, sizeof(stdlibdir));
+    wcscpy_s(stdlibdir, Py_ARRAY_LENGTH(stdlibdir), prefix);
+    /* We initialize with the longest possible path, in case it doesn't fit.
+       This also gives us an initial SEP at stdlibdir[wcslen(prefix)]. */
+    join(stdlibdir, L"lib");
     do {
-        memset(stdlibdir, 0, sizeof(stdlibdir));
-        wcscpy_s(stdlibdir, Py_ARRAY_LENGTH(stdlibdir), prefix);
-        join(stdlibdir, L"lib");
+        assert(stdlibdir[wcslen(prefix)] == SEP);
+        /* Due to reduce() and our initial value, this result
+           is guaranteed to fit. */
+        wcscpy(&stdlibdir[wcslen(prefix) + 1], L"lib");
         if (is_stdlibdir(stdlibdir)) {
             return 1;
         }

From 5db4c3d0e62d125f8a13c710d670ef7ee744cc34 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Fri, 24 Sep 2021 14:11:34 -0600
Subject: [PATCH 11/12] Do not call memset().

---
 PC/getpathp.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/PC/getpathp.c b/PC/getpathp.c
index 6c82db4e9f65a9..38009465ae649c 100644
--- a/PC/getpathp.c
+++ b/PC/getpathp.c
@@ -290,7 +290,6 @@ search_for_prefix(wchar_t *prefix, const wchar_t *argv0_path)
        We guarantee 'prefix' is null terminated in bounds. */
     wcscpy_s(prefix, MAXPATHLEN+1, argv0_path);
     wchar_t stdlibdir[MAXPATHLEN+1];
-    memset(stdlibdir, 0, sizeof(stdlibdir));
     wcscpy_s(stdlibdir, Py_ARRAY_LENGTH(stdlibdir), prefix);
     /* We initialize with the longest possible path, in case it doesn't fit.
        This also gives us an initial SEP at stdlibdir[wcslen(prefix)]. */

From 956cc046b590aa632fdd32e87e24e9ba3c9c4204 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Mon, 27 Sep 2021 09:08:41 -0600
Subject: [PATCH 12/12] Do not check isabs() on Windows.

---
 Python/fileutils.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Python/fileutils.c b/Python/fileutils.c
index 0e7c5b0084411f..2492d0567d84aa 100644
--- a/Python/fileutils.c
+++ b/Python/fileutils.c
@@ -2100,12 +2100,12 @@ static int
 join_relfile(wchar_t *buffer, size_t bufsize,
              const wchar_t *dirname, const wchar_t *relfile)
 {
-    assert(!_Py_isabs(relfile));
 #ifdef MS_WINDOWS
     if (FAILED(PathCchCombineEx(buffer, bufsize, dirname, relfile, 0))) {
         return -1;
     }
 #else
+    assert(!_Py_isabs(relfile));
     size_t dirlen = wcslen(dirname);
     size_t rellen = wcslen(relfile);
     size_t maxlen = bufsize - 1;